Declaration and use of php functions
* Function
* 1. Declaration syntax;
* 2. Calling method;
* 3. Parameter setting;
* 4. Return value;
* 5. Scope
//Declaration
function hello() //无论有无参数,圆括号不能省略 { echo '欢迎来到php中文网学习'; }
//Call: call by name, must bring parentheses
hello(); echo '<hr>'; //可以设置参数 function hello1($siteName) { echo '欢迎来到'.$siteName.'学习'; }
//You must bring parameters when calling now
hello1('php中文网'); hello1('www.php.cn');
//If you forget to give parameters when calling, you can give the function parameters a default value
function hello2($siteName = 'php中文网') { echo '欢迎来到'.$siteName.'学习'; } echo '<hr>';
//You can pass parameters when calling now , you can also pass no parameters
hello2(); echo '<br>'; hello2('PHP中文网_www.php.cn');
//If there are multiple parameters, the default value should be written to the end
function hello3($name ,$siteName = 'php中文网') { echo '我是'.$name.',欢迎来到'.$siteName.'学习'; } echo '<hr>';
//Calling method
hello3('peter zhu'); //第一个参数没有默认值,必须传参 echo '<br>'; hello3('peter zhu', 'www.php.cn'); //实参与形参的位置必须一一对应 echo '<hr>';
//Scope : Function internal variables cannot be accessed from the outside. Similarly, external variables cannot be accessed from inside the function.
$siteName = 'php中文网';
//External variables, or global variables, will automatically become an element in the global variable array $GLOBALS. The variable is The key name of the element
echo $GLOBALS['siteName']; //它里面的数据就是变量siteName中的值,而且这是一个超全局变量,可以在函数中使用 function hello4() { $name = 'peter zhu'; // return $siteName; return $GLOBALS['siteName']; } echo hello4(); echo '<br>'; echo $name; //外部是访问不到函数内的变量的,除非函数将这个变量返回到外部

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